By Mick O'Brien · carpenter & builder · sheds-to-homes, cabins and things that stay up in a storm

“After losing a $12,000 slab to the freeze in 2017, I now insist on insulated radiant heating for every off-grid Aussie cabin I build.”

Forget gas bills. Radiant floor heating is the off-grid heating solution that actually works in Australia. No fluff. Just heat that comes from the ground up. Here's how to do it right.

Solar Thermal Integration: The Only Way to Go

Forget solar PV. For off-grid radiant heating, you need solar thermal collectors. They heat water directly using the sun. No batteries, no inverters. Just hot water flowing through your floor.

Why solar thermal? Because it's 3x cheaper to run than electric or gas. And Australia has the sun. Use it.

Tubing Layout: Don't Mess This Up

Spacing is everything. Too close = wasted money. Too far = cold floors. Stick to 150-200mm between pipes. For a typical 20m² room (like a shed or cabin), you'll need 600-700m of tubing.

Layout pattern: Spiral or snake. Start near the walls. Avoid corners. Run pipes closer to external walls (they lose heat fastest). Use a layout calculator – don't guess.

PEX tubing is the only option. Cheap, flexible, and lasts 50 years. Don't use copper – it's overkill and expensive.

Australian Suppliers & Pricing (indicative prices)

Insulation (MUST HAVE): 50mm rigid foam under the floor. Without it, 50% of heat vanishes into the ground. Price: $300-$400 for 20m².

PEX Tubing (16mm): Plumbline (nationwide). $1.80/m. For 20m² room: ~$1,200.

Solar Thermal Collectors: Sunmaster (Sydney). $1,500 per 2m². For a 20m² room, you need 2-3 collectors. Total: $3,000-$4,500.

Buffer Tank: Rinnai 200L. $1,100. Non-negotiable.

Total DIY Cost (20m² room): $5,600-$6,800. No plumber needed if you're handy.

Real Talk: What Aussies Get Wrong

• Skipping insulation: You'll pay double for heat that never reaches the floor. Don't be that person.
• Using electric underfloor heating: It's a death trap off-grid. Solar thermal is the only viable option.
• Wrong tubing spacing: 300mm spacing = cold feet. 100mm spacing = wasted money. 150mm is gold.
• Not sizing the solar collectors right: Too small = no heat on cloudy days. Size for 3 days of no sun.

Off-grid radiant heating isn't fancy. It's solar thermal, good insulation, and smart tubing. Do it right. Your wallet (and your toes) will thank you.

When to Call a Professional

While many off-grid projects are achievable as DIY, certain situations require licensed professionals:

• Electrical work beyond basic 12V DC additions — requires a licensed electrician
• Structural modifications to buildings or load-bearing elements
• Gas line installation or modification
• Solar array installations above safe voltage thresholds
• Any work that affects the structural integrity of your property

Always check local regulations and obtain necessary permits before commencing work.